Under normal conditions, nature's transport of non-cohesive sub-soil (such as sand) periodically to and onto a beach and off or away from the beach is at--or close to--equilibrium (zero net transport). Seasonal or other variations may tend either to remove sand (erosion by negative net transport) or to replace it (accretion by positive net transport) for substantial periods of time but often average out over a few years if not during each individual year. Beach accretion is hardly ever a cause for concern, but continuing or repeated beach erosion occasions financial and esthetic losses, greatly disturbing landowners, municipalities, tourists, etc.
Beachface dewatering has been known for many years as conducive to accretion, as shown in the technical literature and in patents, such as Vesterby U.S. Pat. No. 4,645,377, Lin U.S. Pat. No. 4,898,495, and more recently in the present inventor's noted U.S. Pat. No. 5,061,117.
Dewatering of the beachface at a level just below mean low water is beneficial by removing part of the overlying water in which non-cohesive subsoil is suspended, thereby increasing the concentration of suspended subsoil in the suspending water, whereupon a bit more of such subsoil than usual is deposited on the beachface during wave onrush and a bit less than usual is removed during the ensuing backwash. Such dewatering need not be continuous but only frequent enough to assure that on the average the beach receives as much sand as it loses--or, if possible, appreciably more than it loses.
Some of the worst beach erosion occurs suddenly, during storms in which great expanses of beach are carried away. The disruptive effect of storms may be ameliorated somewhat by building a beach outward during normal times to provide a buffer or sacrificial zone. Retention of excess sand on the beach so as to appease nature's appetite when on a rampage is generally prudent and much better than periodically dredging up sand and depositing it onto the beach, only to be carried off in a few months. Whether the most violent storms can be neutralized is doubtful, but the present invention extends my previous inventions to enhance day-to-day net accretion, and also to reduce loss from inclement weather effects of diverse magnitudes.